iterating in reverse

[Jonathan P.]

Erik Max Francis <max at alcyone.com> wrote in message news:<3E274D34.8F0C4348 at alcyone.com>...
> "Jonathan P." wrote:
> 
> > Is there an elegant and
> > efficient way to iterate through x in
> > reverse without having to create a reversed
> > copy of it (i.e. y=x[:]; y.reverse())?
> 
> It's not too elegant, but
> 
> 	for j in range(len(x) - 1, -1, -1):
> 	    i = x[j]
> 	    print i

This looks like the best bet so far short of using 2.3.
One thing though, would using xrange instead of range
be preferable?


Chad Netzer wrote:

> Yeah, so you may need to do a copy/reverse  or a 
> reverse/reverse, to keep the original list.

reverse/reverse saves on memory but it implies that 
for reverse() to be a win over a reverse iterator it 
has to be at least twice as fast as the latter.  I
find it very un-Pythonic to have to maintain 2 copies 
of the same list just to be able to access it in 2 
different ways. reverse/reverse feels pretty unPythonic
as well...